Very little is known about the metabolism of divalent metal ions in the lens. This is somewhat surprising considering their content of calcium, magnesium and zinc and the fundamental roles that such metals may play in the life of cells. In addition the levels of Zn are uniquely high in ocular tissues but little is known about the reasons for this. It is planned to study the processes controlling the levels of these metals in the manmalian lens using the isotopes 45Ca and 65Zn and atomic absorption spectrophotometry to trace their accumulation, storage, distribution and losses by the lens. The role of the capsule, anterior epithelium, lens fibers and 'nucleus' will be examined. These metal ions have widespread effects on intermediary metabolism, growth and ion metabolism of tissues. Disturbances related to changes in their availability and regulation could contribute to the appearance of lens opacities and cataracts. They could represent the focus of action of some drugs and cataractous agents on the lens. Hence the pharmacology of these processes will be studied.